Only create PDFs from word processing tools, like Microsoft Word. It may be possible for screen readers to parse text from PDFs created from Word documents.
Don't create PDFs from scanned files of text. It is not possible for screen readers to read these.
Scanned text is not accessible
Use headings and other styles in Microsoft Word. These are made for accessibility! See more on Microsoft’s site.
When you save your Word doc, look for an option that includes the word "Accessibility." This will vary depending on your version of Word. See more on Microsoft’s site.